Espaces de noms
Variantes
Affichages
Actions

Lambda functions (depuis C++11)

De cppreference.com
< cpp‎ | language

This page has been machine-translated from the English version of the wiki using Google Translate.

The translation may contain errors and awkward wording. Hover over text to see the original version. You can help to fix errors and improve the translation. For instructions click here.

Click here for the English version of this page


 
C++
 
Langage C++
Sujets généraux
Contrôle de flux
Instructions conditionnelles
Instructions d'itération
Instructions de saut
Fonctions
déclaration de fonction
expression lambda
fonction générique
spécificateur inline
spécification d'exception (obsolète)
spécificateur noexcept (C++11)
Exceptions
Espaces de noms
Types
spécificateur decltype (C++11)
Qualificatifs
qualificatifs const et volatile
qualificatifs de stockage
qualificatif constexpr (C++11)
qualificatif auto (C++11)
qualificatif alignas (C++11)
Initialisation
Littéraux
Expressions
opérateurs alternatifs
Utilitaires
Types
déclaration typedef
déclaration d'alias de type (C++11)
attributs (C++11)
Jette
Original:
Casts
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
conversions implicites
conversion const_cast
conversion static_cast
conversion dynamic_cast
conversion reinterpret_cast
conversions style C et style fonction
Allocation de mémoire
Classes
Qualificatifs spécifiques aux membres de classe
Fonctions membres spéciales
Modèles
classes génériques
fonctions génériques
spécialisation de modèles
paquets de paramètres (C++11)
Divers
Assembleur
 
Construit une fermeture: un objet fonction anonyme capable de capturer des variables dans la portée.
Original:
Constructs a fermeture: an unnamed function object capable of capturing variables in scope.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Sommaire

[modifier] Syntaxe

[ capture ] ( params ) mutable exception attribute -> ret { body } (1)
[ capture ] ( params ) -> ret { body } (2)
[ capture ] ( params ) { body } (3)
[ capture ] { body } (4)
1)
Déclaration complète
Original:
Full declaration
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
2)
Déclaration d'un lambda const: les objets capturés par copie ne peuvent pas être modifiés .
Original:
Declaration of a const lambda: the objects captured by copy cannot be modified.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
3)
Type de retour omis: le type de retour de la fermeture operator() est déduite d'après les règles suivantes:
Original:
Omitted trailing-return-type: the return type of the closure's operator() is deduced according to the following rules:
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
  • si le body est composé de la mention return unique, le type de retour est le type de l'expression retournée (après conversion implicite rvalue-à-lvalue, tableau à pointeur, ou fonction-à-pointeur)
    Original:
    if the body consists of the single return statement, the return type is the type of the returned expression (after rvalue-to-lvalue, array-to-pointer, or function-to-pointer implicit conversion)
    The text has been machine-translated via Google Translate.
    You can help to correct and verify the translation. Click here for instructions.
  • autrement, le type de retour est void
    Original:
    otherwise, the return type is void
    The text has been machine-translated via Google Translate.
    You can help to correct and verify the translation. Click here for instructions.
4)
Liste des paramètres omis: la fonction ne prend aucun argument, comme si la liste des paramètres est ()
Original:
Omitted parameter list: function takes no arguments, as if the parameter list was ()
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

[modifier] Explication

mutable - Permet à
body de modifier les paramètres capturés par copie, et d'appeler leurs fonctions de membre non-const
Original:
allows body to modify the parameters captured by copy, and to call their non-const member functions
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
exception -
fournit la spécification d'exception ou la noexcept clause pour l'opérateur () du type de fermeture
Original:
provides the spécification d'exception or the noexcept clause for operator() of the closure type
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
attribute -
fournit à l'opérateur la spécification d'attribut () du type de fermeture
Original:
provides the spécification d'attribut for operator() of the closure type
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
capture -
spécifie les symboles visibles dans le champ où la fonction est déclarée sera visible à l'intérieur du corps de la fonction.
Original:
{{{2}}}
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Une liste de symboles peut être adoptée comme suit:

  • [a,&b] où a est capturé par valeur et b est capturé par référence.
  • [this] capte le pointeur this
  • [&] captures all symbols by reference
  • [=] captures all by value
  • [] captures nothing
params -
La liste des paramètres, comme dans nommée fonctions
Original:
The list of parameters, as in nommée fonctions
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
ret -
Type de retour. S'il n'est pas présent il est implicite dans les énoncés de retour de fonction (ou void si elle ne retourne aucune valeur)
Original:
Return type. If not present it's implied by the function return statements ( or void if it doesn't return any value)
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
body -
Corps de la fonction
Original:
Function body
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.


L'expression lambda construit un objet non identifié temporaire unique, anonyme non syndiqué non agrégée type, connu sous le nom' type de fermeture, ce qui comprend les membres suivants:
Original:
The lambda expression constructs an unnamed temporary object of unique unnamed non-union non-aggregate type, known as closure type, which has the following members:
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

ClosureType ::
Original:
ClosureType::
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
operator()

ret operator()(params) const { body }
 (
le mot-clé mutable n'a pas été utilisé
Original:
the keyword mutable was not used
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
)
ret operator()(params) { body }
 (
le mot-clé mutable a été utilisé
Original:
the keyword mutable was used
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
)

Executes the body of the lambda-expression, when invoked. When accessing a variable, accesses its captured copy (for the entities captured by copy), or the original object (for the entities captured by reference). Unless the keyword mutable was used in the lamda-expression, the objects that were captured by copy are non-modifiable from inside this operator().

Dangling references

If an entity is captured by reference, implicitly or explicitly, and the function call operator of the closure object is invoked after the entity's lifetime has ended, undefined behavior occurs. The C++ closures do not extend the lifetimes of the captured references.

ClosureType ::
Original:
ClosureType::
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
operator ret(*)(params)

typedef ret(*F)(params);
operator F() const;

This member function is only defined if the capture list of the lambda-expression is empty.

The value returned by this conversion function is a function pointer that, when invoked, has the same effect as invoking the closure object's function call operator directly.

ClosureType ::
Original:
ClosureType::
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
ClosureType()

ClosureType() = delete;
ClosureType(const ClosureType& ) = default;
ClosureType(ClosureType&& ) = default;

Closure types are not DefaultConstructible. The copy constructor and the move constructor are implicitly-declared and may be implicitly-defined according to the usual rules for implicit copier des constructeurs and déplacer des constructeurs.

ClosureType ::
Original:
ClosureType::
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
operator=()

ClosureType& operator=(const ClosureType&) = delete;

Closure types are not CopyAssignable.

ClosureType ::
Original:
ClosureType::
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
~ClosureType()

~ClosureType() = default;

The destructor is implicitly-declared.

ClosureType ::
Original:
ClosureType::
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
CapturedParam

T1 a;

T2 b;

...

If the lambda-expression captures anything by copy (either implicitly with capture clause [=] or explicitly with a capture that does not include the character &, e.g. [a, b, c]), the closure type includes unnamed non-static data members, declared in unspecified order, that hold copies of all entities that were so captured.

The type of each data member is the type of the corresponding captured entity, except if the entity has reference type (in that case, references to functions are captured as-is, and references to objects are captured as copies of the referenced objects).

For the entities that are captured by reference (with the default capture [&] or when using the character &, e.g. [&a, &b, &c]), it is unspecified if additional data members are declared in the closure type.

This section is incomplete
Reason: scope rules, capture list rules, nested lambdas, implicit capture vs odr use, decltype

[modifier] Exemple

Cet exemple montre comment passer un lambda à un algorithme générique et que les objets résultant d'une déclaration lambda, peuvent être stockés dans des objets std::function .
Original:
This example shows how to pass a lambda to a generic algorithm and that objects resulting from a lambda declaration, can be stored in std::function objects.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

#include <vector>
#include <iostream>
#include <algorithm>
#include <functional>
 
int main()
{
    std::vector<int> c { 1,2,3,4,5,6,7 };
    int x = 5;
    c.erase(std::remove_if(c.begin(), c.end(), [x](int n) { return n < x; } ), c.end());
 
    std::cout << "c: ";
    for (auto i: c) {
        std::cout << i << ' ';
    }
    std::cout << '\n';
 
    std::function<int (int)> func = [](int i) { return i+4; };
    std::cout << "func: " << func(6) << '\n'; 
}

Résultat : 

c: 5 6 7
func: 10

[modifier] Voir aussi

auto spécificateur
spécifie un type défini par l'expression (C++11)
Original:
specifies a type defined by an expression (C++11)
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
[edit]
(C++11)
 adaptateur générique de foncteur
(classe générique) [edit]
Récupérée de « https://fr.cppreference.com/mwiki/index.php?title=cpp/language/lambda&oldid=50074 »